Magnetic control of electric arcs by means of permanent magnets attached to the electrode holder



June 10, 1969 E. H RINGTON 3,449,610

MAGNETIC CONTROL ELECTR ARCS BY MEANS OF PERMANENT MAGNETS ATTACHED TO THE ELECTRODE HOLDER Filed June 2, 1967 iIILH' w Ag INVENTOR ROGER E. HARRINGTON United States Patent U.S. Cl. 313-32 7 Claims ABSTRACT OF THE DISCLOSURE An arc illumination system which incorporates a magnetic material to offset the undesirable self-induced magnetic phenomena in the area of the arc. The magnetic material is placed in intimate contact with the positive electrode holder and is cooled substantially solely by virtue of its contact therewith.

BACKGROUND OF THE INVENTION Field of the invention The instant invention relates generally to electric arc systems which are used primarily for illumination purposes and more specifically to an improved manner of controlling the arc by altering the magnetic field in the vicinity of the arc.

Description of the prior art It is well known that an are which is struck between two electrodes commonly employed in illumination devices is quite sensitive to the self-induced magnetic field positioned around the arc and the electrodes. For example, the arc is pushed outward by its own magnetic field in the direction of the bisection of the angle between the electrodes. This deviation of the arc is not without effect. At high amperage operation, for instance, maintenance of a stable arc is virtually impossible. Furthermore, since the arc current to the anode must travel circuitously through the deviated arc stream, are voltage and wattage must be maintained at unnecessarily high levels.

To overcome these and other similar disadvantages, it has been proposed that a separately induced magnetic field having a direction which is perpendicular to the plane of the arc electrodes be introduced into the arc system. In this manner, the adverse effects of the selfinduced magnetic field may be partially or totally neutralized b the external field. While this theory has been successfully tested in the laboratory, practical commercial implementation has been difiicult primarily due to the adverse influence of the intense are heat. The use of a coil-less horseshoe magnet has been attempted but with only partial success since the magnet must necessarily be placed proximate the arc and since the magnetic effect of iron decreases rapidly with increase in temperature. Air cooling of the magnetic affords only slight improvement.

A recently issued patent, U.S. Patent 3,244,931, is directed to a system substantially similar to that abovedescribed. In this system, the patentee employs two parallel copper tubes which are symmetrically placed with respect to the arc and through each of which a current flows in a direction such that a neutralizing magnetic field is produced. The copper tubes are partially cooled by means of a fluid passing .therethrough. However, since the tubes are adjacent the arc, they must be coated with a heat resistant, electrically insulating material to avoid malfunction and deterioration due to the surrounding high temperature. This system, while apparently somewhat successful, is unnecessarily complex and expensive.

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SUMMARY OF THE INVENTION It is the primary object of this invention to provide an arc illumination system of the type hereinbefore discussed wherein the magnetic material is cooled in an efficiently simple manner such that said material is substantially unaffected by the heat of the arc.

Broadly, the invention comprises positioning a magnetic material on the holder in which the arc electrode is secured. The magnetic material is cooled substantially solely because of its intimate contact with the holder which is itself being cooled. In this manner, separate individual cooling or coating of the magnetic material is not required, thereby permitting the desired external magnetic effects to be generated in a most economical way.

It will be appreciated as the invention is more specifically described hereinafter that the magnetic material must have a substantial portion thereof in contact with the electrode holder and, furthermore, must not be unduly projected into the area surrounding the arc. Of equivalent importance are the requirements that the electrode holder be satisfactorily cooled and that it be composed of a material which readily absorbs the heat from the mag netic material.

More specifically, the invention is directed to an arc system wherein the positive electrode holder is composed of a material such as silver, is cooled by means of a fluid, preferably such as water, and is in contact with a magnetic material such as iron. The iron or equivalent may be secured to the holder by soldering, brazing or the like. The fluid which cools the holder also cools the magnetic material either with or without direct contact will hereinafter be described in greater detail.

By the term magnetic material is meant any material which either generates a magnetic field or induces a variation in the existing magnetic field surrounding the arc. The term is intended to include permanent magnets of all types as well as inducing materials such as soft iron or cold rolled steel.

It is well known that a current carrying component generates a magnetic field which encircles the component. This phenomenon is clearly present in an arc illumination system, since the electrodes between which the arc is maintained are current carrying components. As hereinbefore mentioned, the magnetic field in the area of the arc produces undesirable effects such as a net force which deviates the arc.

In the instant invention, if a permanent magnet or other magnetic field producing material is properly positioned on an electrode holder, a magnetic field will be generated which, when combined with the magnetic field in the area of the arc, produces a force which tends to correct the arc position. Such a force results from the interaction of the externally generated essentially unidirectional field and the encircling fields of the current components. The unidirectional field adds to and increases the strength of the portion of the encircling field which is in the same direction and neutralizes the portion of the encircling field which is in the opposite direction, thereby producing a force having a direction from the strengthened to the weakened area. This force erects the arc.

If a magnetic inducing material is properly positioned on an electrode holder, its presence in the magnetic field of the arc will cause the field to be distorted; that is, the field will be attracted to the inducing material causing a greater distortion in the circular field proximate the inducing material. The distortion produces a net force in the direction of the inducing material which tends to correct the arc position. In this manner, the necessary force is produced by an inductive process.

The strength of the magnetic field which is produced by the arc stream current is proportional to the are current. The position of the arc is a function of several variables including the field strength and therefore the self-induced deviating force, as well as the external force added by convective air fiow past the arc. When an external field is generated or an inducing material is placed near the arc and the arc begins to correct itself, another variable is introduced; that is, the original force on the encircling field is reduced and thus the current is somewhat reduced. It will be appreciated, therefore, that the exact quantity of magnetic inducing material employed or the strength of the field generated by the magnetic producing material will depend on an adjustment for all of these variables, but that it is well within the skill of the practicing artisan to provide for these adjustments in order to correct the position of the arc.

Of course, if the net force is to be varied, it can readily be increased or decreased by providing more or less field inducing or producing material. In addition, the distance of the magnetic material from the arc may also be controlled in order to vary the net force. It has been discovered that by placing the magnetic material on the electrode holder, a properly controlled distance may easily be achieved.

The direction of the net force can be controlled by properly positioning the magnetic material on the electrode holder. Normally, excellent results are obtained if the magnetic material is positioned below the arc, since the net force will tend to pull the tip of the arc downward and generally toward the magnetic material, thereby actually erecting the arc. Thus, if magnetic material is placed above the are, additional material should be added below the arc to compensate and to produce the desired effect.

In addition, excellent effects are obtained when the magnetic material is symmetrically situated with respect to the arc; that is, if several pieces of magnetic material are employed, they should be properly balanced so that the net force is in the direction desired.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is clearly illustrated in the following drawing wherein:

FIGURE 1 is a side elevation view of a portion of an arc illumination system typically employed in the invention;

FIGURE 2 is a front elevation view of a positive electrode holder having a field producing magnetic material afiixed thereto;

FIGURE 3 is a plan view of the holder illustrated in FIGURE 2;

FIGURE 4 is a front elevation view of a positive electrode holder representing another embodiment of the invention; and,

FIGURE 5 is a side elevation view of the holder of FIGURE 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing, there is shown in FIG- URE 1 an arc illumination system comprising a positive electrode 12 and a negative electrode 14 which are inclined at an angle of greater than 0 and less than 90, usually between 50 and 80. An arc flame or stream 16 is formed in the area between electrodes and is constantly maintained throughout the operation of the system. The electrode 12 is positioned in a holder 18 which includes an upper jaw 20 and alower jaw 22. A magnetic material 24 is secured to the lower jaw 22 on its front end face 26.

The effect produced by the magnetic material 24 on the flame 16 is illustrated by the dashed lines 28 which show that the position of the arc stream is altered, that is, the tip of the flame is moved to a more nearly vertical position. To offset possible instability, the negative electrode 14 is also repositioned (illustrated by the dashed FIGURE 30) along a locus of constant distance from the tip of the negative electrode 14 to the center of the positive crater (not shown).

FIGURES 2 and 3 more clearly depict the positioning of a magnetic material on the lower jaw of an electrode holder. In FIGURE 2, a silver holder 32, composed of upper jaw 34 and lower jaw 36 is covered across its front end face 38 by a plate 40 which may be suitably composed of brass or similar material. A plate 42 of magnetic material such as iron is secured to the brass plate 40 on the lower jaw 36. As shown in FIGURE 3, the iron plate 42 projects only slightly beyond the front end face 38 and the brass plate 40. The plate 40 may be employed if a recess is machined in the holder jaw and during the machining process the channels (58, 60 in FIGURE 5) containing the coolant material are exposed The plate is then used to partially or totally reseal the channels.

It will, therefore, be appreciated from a review of FIGURES 1-3 that similar desirable effects heretofore achieved by the use of an external magnetic field produced by cumbersome equipment may be easily accomplished in the manner illustrated. It may be further observed that the magnetic material, being in intimate contact with the electrode holder, may be easily cooled thereby.

The electrode holder may be cooled in a great many ways, the preferable method being that set forth in my copending US. application, Ser. No. 385,120 entitled A Method for Producing High Brightness and Lower Electrode Consumption Rate in Carbon Arcs, filed July 27, 1964. In that application, the electrode jaws are generally hollow and a liquid .such as water or ethylene glycol is passed therethrough. It is apparent that if such a method of cooling were employed in the instant invention, the internal liquid would readily cool the magnetic producing material placed on any surface of the jaws provided said material did not extend too far beyond the jaw surface to which it is affixed.

The embodiment of the invention illustrated in FIG- URES 1-3 was tested in order to determine its effectiveness. Several types of positive carbon electrodes were used, one being designated as Ultrex and the other as Ultrex 300. Both types were constructed with a shell and a core, the shell being composed of graphite and the core having graphite and rare-earth salts as its ingredients. The Ultrex is differentiated from the U1- trex 300 in the size of the core, the former having a diameter of 0.238" and the latter a diameter 0.286".

The negative electrodes used in the tests were composed of graphite. These negative electrodes were maintained at a distance of inch from the center of the positive electrode crater, while the positive electrode protruded inch from the front end face of the electrode holder. The jaws were made of silver and were internally cooled with water. A circular iron plate having a maximum thickness of one millimeter and having a length of about 1 inch and a width of about /2 inch was soldered onto the lower jaw of the positive electrode holder as indicated in FIGURE 2. The distance from the center of the iron to the bottom of the positive electrode face was approximately /2 inch.

The following table sets forth data obtained during these tests.

Brightness (c./mn. Consump- Magnetlc I tion rate Arc powe Figure of Test No material Positive carbon ,1 (amps) V (volts) Center Average (i.p.h.) (kw.) merit Ultrex 205 77. 8 1, 880 970 74. 6 15. 8 398 Ultrex 207 81. 8 2, 215 1, 060 81. 5 16. 8 456 322 82.0 2, 220 1, 340 I52 26. 4 385 300 295 80.9 2, 200 1, 335 122 23. 7 426 Ultrex 197 76. 6 1, 800 925 67. 5 15. 0 400 Ultrex 181 75. 4 1, 800 880 53. 5 13. 7 461 Figure of Merit is Center brightness X Power Consumption rate. Improved carbon performance gives larger number.

As shown in the table, either a greater center brightness or a lower consumption rate was achieved in all of the test runs when a magnetic material was used. The Figure of Merit, which is a good indication of the overall performance of the are system, illustrates the clear advantage of using the magnetic material and more importantly indicates how little effect, if any, the heat of the arc has on the magnetic material when it is cooled in accordance with the teachings of this invention. It is to be noted that the magnetic material required no coating or other cooling and yet the increase in performance was as high as 18% for center brightness and 20% lower consumption rate.

The magnetic material need not be iron but may be any material capable of inducing or generating strong enough magnetic effects. Examples of other suitable ferromagnetic materials which can be used to provide the magnetic field effects are nickel, cobalt and alloys of iron, nickel and cobalt.

As illustrated in FIGURES 4 and in the drawings, the magnetic material 42 may be placed on both the upper jaw 44 and lower jaw 46 of the holder 48, it being preferable to place about twice as much material 42 on the lower jaw 46. It will also be noted that both jaws 44, 46 are provided with recesses 50, 52. In this manner, a thicker quantity of magnetic material may be employed as required and yet still not be unduly projected into the area of the arc. Orifices 54, 56 (FIGURE 5) accept the fluid coolant into the holder from conduits (not shown). The coolant then flows through channels 58, 60 and egresses at the opposite side of the holder jaws. Openings 62 and 64 may be provided to permit direct contact between the fluid and the magnetic material to improve the cooling efiiciency.

It will be appreciated that while preferred embodiments have been hereinbefore described, variations and modifications of the instant invention are well within the practitioners skill. For example, a threaded screw composed of iron could be inserted into a threaded hole in the holder and fixed in place. With this construction, the projection of the iron beyond the front end face of the holder can be carefully controlled.

What is claimed is:

1. An arc illumination system comprising:

(a) light generating means including a positive electrode and a negative electrode, said electrodes being capable of maintaining an are intermediate adjacent ends thereof;

(b) an electrode holder in communication with at least one of said electrodes to maintain said electrode in an arc supporting position;

(c) cooling means for cooling said electrode holder;

((1) a magnetic material affixed to at least one surface of said holder, said material being capable of varying the self-induced magnetic force in the vicinity of said arc, said magnetic material being cooled by said holder cooling means, the projection of said material toward said are being limited substantially to said surface such that, in operation, said material is substantially unaffected by the heat of said arc.

2. The system of claim 1 wherein said electrode holder is internally cooled by the passage of a fluid therethrough.

3. The system of claim 2 wherein said magnetic material is selected from the group consisting of iron, cobalt, nickel an alloys thereof.

4. The system of claim 2 wherein said holder comprises an upper and lower jaw, is composed of silver and and is in communication with said positive electrode.

5. The system of claim 4 wherein said iron is secured to said lower jaw in a position such that it is symmetrically located with respect to said arc so that the resultant magnetic force on said are is in a direction to erect said arc.

6. The system of claim 2 wherein said cooling fluid is Water.

7. The system of claim 1 wherein said magnetic material is cooled substantially solely because of its contact with said surface.

References Cited UNITED STATES PATENTS 917,200 4/1909 Viertel 313-153 1,353,993 9/1920 Yorke 313-153 2,107,148 2/1938 Gretener 3l420 2,115,688 4/1938 McAuley 31420 X 2,608,675 8/1952 Buckingham 31420 X 2,957,108 10/1960 Harrington 31420 X 3,244,931 4/1966 LeVantine et al. 313-153 X JAMES W. LAWRENCE, Primary Examiner. C, R. CAMPBELL, Assistant Examiner.

US. Cl. X.R. 

